Diagnosis: Test rounded, ovoid or elongated elliptical or flask shaped, laterally compressed, aperture variable from linear to strongly curved, with or without thickened lip. Test hyaline or slightly yellowish, with a smooth organic surface (exception: Hyalosphenia punctata which has a punctuated surface). Type species: Hyalosphenia cuneata (Stein) Schulze. 20 species are considered as valid, among which many are problematic and need molecular data to confirm their position within the genus.

Key to the species

1

Test with a distinct neck

2

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Test without distinct neck, rounded, ovoid, or elongated elliptical

9

2

Neck long, test flask- or bottle-shaped

3

–

Neck very short

6

3

Lateral margin of test not smooth

4

–

Lateral margin of test smooth or slightly wavy

5

4

Main part of test with round to oval depressions, giving the outline a inrregularwavy apprearance, L=(68)85-110(130)μm, B=40-65 μm, aperture curved, with a well-developed 15-20 μm wide organic collar

H. elegans

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Round to oval depressions not limited to the main part of the test but extending toward the neck